Machine for grinding ceilings



March 2, 1954 P. F. MCDON-OQUGH MACHINE FOR GRINDING CEILINGS Filed Sept. 13, 1951 INVENTOR. Paul lz'Mc Donough BY 09129 Patented Mar. 2, 1954 I MACHINE FOR GRINDING GEILINGS Paul F. McDonough, Dorchester, Mass. Application September 13, 1951, Serial No. 246,361

This invention has to do with machines for grinding or surfacing concrete ceilings. l-Ieretofore machines have been made for this purpose, but such machines are heavy, cumbersome, difficult to operate, and therefore have not been commonly employed. I have discovered, however, that it is possible to construct a machine which is easily movable from one place .to another, can be adjusted very quickly for differences in ceiling heights and which will operate rapidly and effectively. The invention will be fully-understood from the accompanying drawings in which:

.Fig. 1 is a view in perspective of the machine embodying my invention;

Fig. 2 is a View on a smaller scale indicating the manner in which the grinding element is moved vertically and adjusted; and,

Fig. 3 is a detail of the mounting for the grinding element.

Referring now to the drawings, the machine is conveniently mounted on a triangular base II and swivelling casters I2. Projecting upwardly from the base are three legs l3, l4 and I5 which support a top H5 in which is mounted a tube II. This tube is held rigid by braces Hi. The foregoing parts together form a standard for the moving parts of the device. In the tube I1 is a vertically slidable rod l9 having on its top a fixed axis member 20 which is in the form of a tube. The rod l9 may be slid up and down in the tube I1 and fixed in the desired position of adjustment by clamp screws 1, 1. Within the axis member 20 is a rod 2! forming one side of a rectangular frame A composed of two side members 22-22 and a cross bar 23. The cross bar 23 is pivoted in bushings 24 on the ends of the side members 22-22 so that the grinding element D which is mounted on the cross bar may tilt as will be described hereafter.

Extending from the leg I3 to the leg M of the fixed standard is an axis member 26 which acts as a brace for the legs and also as an axis for a frame B composed of two side members 21-2l, a cross member 28 which forms a handle by which the frame may be tilted on its axis, and a pivotal member 29 connecting the two legs 2'|--2'|. The pivotal member 29 extends through bushings 30-30 on the ends of the legs 2'l-2l and is connected to two struts C, each of which is composed of a tubular member 3| and a rod 32 telescoped within the tubular member 3!.

Clamping screws 34 are provided to lock the two parts together in adjusted position. At the top the rods 32-32 which form part of the struts 4 Claims. (Cl. 51-180) C are connected to the bushings 24 on the projecting ends of the cross bar 23 of the frame A on which the grinding element D is mounted.

In effect, therefore, the machine includes an upper frame A and a lower frame B pivoted on the respective upper and lower :axis of members 20 and 26 on the vertical standard and linked together by the strut C to form a parallel motion. Springs 35 and 36 connected at their top to the frame A and at their bottom to the frame B are provided to compensate for the weight of the grinding element 1'.) and the frames A and B and relieve the operator of most of the effort of holding the grinding element against the ceiling. A third spring 38 is connected at the bottom to the frame 13 and at its upper end to the top It. This spring is preferably a closed coil I and strong enough to hold the parts in the position shown in' Fig. 1 when the machine is not in use.

The grinding element D is driven by a suitable power unit 40 conveniently located on the base and connected to the grinding element by a flexible shaft 4| enclosed in a tubular sheath 42. The grinding element is secured to the shaft 4| which is rotatably mounted in a sleeve 44. This sleeve is mounted on a cross-axis 46, the ends of which are received in holes in a ring 41, and this ring 41 is itself mounted so that it can tilt on the cross bar 23.

In using the machine, the top frame A is raised until the grinding element D is almost in contact with the ceiling to be surfaced. This is accomplished by loosening the clamping screw 1 and tightening it again when the grinding element has been raised to the proper height and then loosening the screws 34 to adjust the height of the handle 28 after which they are tightened. The operator then starts the motor v of the power unit and bears down on the handle 28 of the lower frame B, which, in turn, raises the grinding element and presses it against the celling with whatever force the operator chooses to exert. He moves the machine about from place to place as the work progresses. This can be done easily by the handle 28 and the casters l2.

If it is desired to surface a vertical surface such as the side of a beam, the flexible shaft 42 is carried up over the upper axis member 20 and reconnected with the grinding element in substantially vertical position. In this position the grinding unit is pushed against the wall and raised and lowered by the handle 28 as the work progresses. In either position, whether horizontal for a ceiling or vertical for a beam or the like, the face of the grinding element assumes automatically a position parallel to the surface to be operated upon, this being permitted by the universal joint on which it is mounted.

Iclaim:

1. A grinding machine for surfacing concrete ceilings comprising a vertical standard, upper and lower horizontal axis members fixedly mounted on the standard, an upper frame pivoted on the upper :aXis member, a lower frame pivoted on the lower axis member, a strut connecting the two frames and forming with them and the vertical standard a parallel motion in which the frames move up anddow-n around their respective upper and lower axes, a rotatable grinding element on the upper frame and a handle on the lower frame whereby movement of the handle moves the grinding element in a vertical direction.

2. A grinding machine for surfacing concrete ceilings comprising a vertical standard, upper and lower horizontal axis members fixedly mounted on the standard, an upper frame pivoted on the upper axis member, a lower frame pivoted .on the lower axis member, a strut connecting the two frames and forming with them and the .vertical standard a parallel motion in which the frames move up and down around their respective upper and lower axes, a rotatable guiding element on the upper frame and a handle on the lower fram whereby movement of the handle moves the grinding element in a vertical direction, amotor and a flexible shaft connecting the motor and the grinding element, and a compensating spring tending to hold the frames in horizontal position.

3 Agrinding machine for surfacing concrete ceiling comprising a vertical standard, upper and lower horizontal axis members fixedly mounted on the standard, an upper frame pivcted on the upper axis member, a lower frame pivoted on the lower axis member, a strut connecting the two frames and forming with them and the vertical standard a parallel motion in which the frames move up and down around their respective upper and lower axes, a rotatable grinding element on the upper frame and a handle on the lower frame whereby movement of the handle moves the grinding element in a vertical direction and the standard and the strut being adjustable longitudinally.

4. A grinding machine for surfacing concrete ceilings comprising a vertical standard, upper and lower horizontal axis members fixedly mounted on the standard, an upper frame pivoted on the upper axis member, a lower frame pivoted .on the lower axis member, a strut connecting the two frames and forming with them and the vertical standard a parallel motion in which the frames move up and down around their respective upper and lower axes, a rotatable grinding element on the upper frame and a handle on the lower frame whereby movement of the handle moves the grinding element in a vertical direction and a joint for universal movement supporting the grinding element on the upper frame.

PAUL F. McDONOUGH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,044,423 Rosa Nov. 12, 1912 1,134,925 Soderlund Apr. 6, 1915 1,561,250 Kunze Nov. 10, 1925 2,049,935 Woodward Aug. '4, 1936 2,093,289 Obherg Sept. '14, 1937 2,124,705 Locklin July '26, 1938 2,484,906 Pond et a1 Oct. 18,, I949 

